1. Field of the Invention
The present invention relates to a process for the manufacture of a hollow turbomachine blade, particularly a large chord fan rotor blade, and to a multiple-action furnace press for use in the process.
The advantages of using large chord blades in turbomachines are particularly apparent in the case of the fan rotor blades in bypass turbo jet engines. However, such blades must cope with severe conditions of use and, in particular, must possess satisfactory mechanical characteristics combined with anti-vibration properties and resistance to impact by foreign bodies. The need to achieve sufficient speeds at the tips of the blades has also led to seeking a reduction in the mass of the blades, and this has been achieved, in particular, by using hollow blades.
2. Summary of the Prior Art
EP-A-0700738 describes a process for the manufacture of a hollow turbomachine blade, especially a fan rotor blade having a large chord. In a first stage (a) of this process a computer-aided design and manufacturing (CAD/CAM) system is used to create, starting from a geometric definition of the blade to be obtained, a digital simulation consisting of computing for the constituent parts of the blade, on both sides of the central fibre, the lengths of the fibres as a function of their position relative to the axis 20 of the respective part 19 as shown in FIG. 1, the parts being flattened. Also carried out at this stage is a digital simulation of an operation to shape the parts by twisting, for comparison with the final result.
After this first stage the manufacturing process known from EP-A0700738 involves the following steps:
(b) die-forging the primary parts of the blade in a press. PA1 (c) machining the primary parts; PA1 (d) depositing diffusion barriers on at least one of the parts according to a predefined pattern; PA1 (e) assembling the primary parts and diffusion welding them together under isostatic pressure; PA1 (f) inflating the welded assembly using pressurized gas and superplastic shaping the assembly; and, PA1 (g) final machining of the shaped assembly
One of the aims of the invention is to make it possible to perform, during the above sequence of operations, an additional shaping of the parts by twisting, without any risk of causing buckling type corrugations along the central fibre. These corrugations are generated by compression stresses induced at the time of the elongation of the lateral fibres resulting from the length differences between the initial flat part and the twisted part.